Gain of alternative functions promoted by structural changes in redox metalloproteins

DAMIAN ALVAREZ-PAGGI; SANTIAGO OVIEDO ROUCO; DANIEL H. MURGIDA; MARIA ANA CASTRO; RAFAEL RADI

Groningen

Simposio; 14th International Symposium on Biocatalysis and Biotransformations; 2019

Redox metalloproteins are involved in numerous electron transfer (ET) and catalytic biological processes such as cellular respiration, metabolism, molecular signalling and photosynthesis among others. Much effort has been done in order to understand the factors that determine the loss and gain of function of redox proteins in order to improve their use in biodevices. Here, we present an example where different changes in the protein environment and / or post-translational modifications induce structural changes at the level of the metal site that result in an increase in activity. Molecular dynamics and hybrid QMMM simulations were used in combination with UV-Vis, electrochemical and time-resolved SERR (surface-enhanced Resonance Raman) spectroelectrochemical experiments.Cytochrome c (Cyt) is a soluble hemoprotein capable of developing more than one function. We studied the effect of tyrosine nitration and electrostatic interactions on selected Cyt mutants (Y67F, E66Q). Although there is no direct interaction between these mutated residues and the heme group, these variants show different kinetic ET parameters than the native protein and they show a differential response when subjected to different electric fields. Furthermore, tyrosine 74 nitration which triggers a loss of electron shuttling capability, concomitant gain of peroxidatic activity and an early alkaline transition in native Cyt, did not show the same response in the Y67F mutant. Our computational simulation studies suggest that a disruption of the hydrogen bond network is responsible for these effects, evidencing how second sphere perturbations may affect the enzymatic and catalytic response of native proteins